400ex compression

[Tyle]

I was wondering if I could run a JE 12.5 to 1 compressoin piston on my 400ex without out having to install larger studs or having head gasket problems.

[yamaha killa]

i wouldn't...my friend tried a 13:1 and bent the rod and twisted the crank. u'd be safe sticking around a 11:1

[frogburner]

I wouldnt try it.. If you dont want to change the studs or rod, stay with 11:1. I bent my stock rod with a 11:1 406,, so I went big, and love every bit of it.. so pay attention to your bikes performance either way. If you dont beef up things when you go bigger, they bend and break after a while..